CVE-2026-2325

Mattermost versions 11.5.x = 11.5.1, 10.11.x = 10.11.13, 11.4.x = 11.4.3 fail to limit the size of the request body on the start meeting API endpoint, which allows an authenticated attacker to cause resource exhaustion or denial of service via a crafted oversized HTTP POST request to...

EUVD-2026-30753

Mattermost versions 11.5.x = 11.5.1 fail to verify channel membership when processing AI-assisted message rewrites which allows an authenticated attacker to read the content of threads in private channels and direct messages they do not have access to via a crafted request to the post rewrite...

CVE-2026-5163

Mattermost 11.5.x prior to 11.5.2 (up to 11.5.1 affected) fails to verify channel membership when processing AI-assisted message rewrites, allowing an authenticated user to read content from threads in private channels and direct messages they should not access via a crafted request to the post r...

CVE-2026-5163 Missing authorization check in AI message rewrite endpoint allows access to private thread content

Mattermost versions 11.5.x = 11.5.1 fail to verify channel membership when processing AI-assisted message rewrites which allows an authenticated attacker to read the content of threads in private channels and direct messages they do not have access to via a crafted request to the post rewrite...

CVE-2026-5163

Mattermost versions 11.5.x = 11.5.1 fail to verify channel membership when processing AI-assisted message rewrites which allows an authenticated attacker to read the content of threads in private channels and direct messages they do not have access to via a crafted request to the post rewrite...

CVE-2026-5163 Missing authorization check in AI message rewrite endpoint allows access to private thread content

Mattermost versions 11.5.x = 11.5.1 fail to verify channel membership when processing AI-assisted message rewrites which allows an authenticated attacker to read the content of threads in private channels and direct messages they do not have access to via a crafted request to the post rewrite...

CVE-2026-5163 Missing authorization check in AI message rewrite endpoint allows access to private thread content

Mattermost versions 11.5.x = 11.5.1 fail to verify channel membership when processing AI-assisted message rewrites which allows an authenticated attacker to read the content of threads in private channels and direct messages they do not have access to via a crafted request to the post rewrite...

CVE-2026-3117

Mattermost plugins contain a permission-check flaw in the GitLab plugin command processing. Versions affected: Mattermost Plugins

CVE-2026-3117

Mattermost Plugins versions =11.5 11.1.5 10.13.11 11.3.4.0 fail to properly check for permissions when processing commands in the Gitlab plugin which allows normal users to uninstall instances or setup webhook connections via the gitlab instance option or the /gitlab webhook option commands...

CVE-2026-3117 Instance and webhook GitLab plugin commands were able to be run by non-admin users

Mattermost Plugins versions =11.5 11.1.5 10.13.11 11.3.4.0 fail to properly check for permissions when processing commands in the Gitlab plugin which allows normal users to uninstall instances or setup webhook connections via the gitlab instance option or the /gitlab webhook option commands...

EUVD-2026-30748

Mattermost Plugins versions =11.5 11.1.5 10.13.11 11.3.4.0 fail to properly check for permissions when processing commands in the Gitlab plugin which allows normal users to uninstall instances or setup webhook connections via the gitlab instance option or the /gitlab webhook option commands...

CVE-2026-4286

Mattermost versions 11.5.x = 11.5.1, 10.11.x = 10.11.13 fail to check if teamid was being changed when updating playbooks, allowing users with only Manage Playbook Configurations permission to change a playbook's team, bypassing manage members restriction via PUT api. Mattermost Advisory ID:...

CVE-2026-4286

Mattermost Playbooks plugin vulnerability CVE-2026-4286 affects Mattermost versions 11.5.x <= 11.5.1 and 10.11.x

CVE-2026-4286 Playbooks Plugin fails to validate team transfers, allowing unauthorized removal of member access via playbook update

Mattermost versions 11.5.x = 11.5.1, 10.11.x = 10.11.13 fail to check if teamid was being changed when updating playbooks, allowing users with only Manage Playbook Configurations permission to change a playbook's team, bypassing manage members restriction via PUT api. Mattermost Advisory ID:...

CVE-2026-4286 Playbooks Plugin fails to validate team transfers, allowing unauthorized removal of member access via playbook update

Mattermost versions 11.5.x = 11.5.1, 10.11.x = 10.11.13 fail to check if teamid was being changed when updating playbooks, allowing users with only Manage Playbook Configurations permission to change a playbook's team, bypassing manage members restriction via PUT api. Mattermost Advisory ID:...

CVE-2026-6339 Missing request origin validation on burn-on-read reveal endpoint

Mattermost versions 11.5.x = 11.5.1, 11.4.x = 11.4.3 fail to validate the X-Requested-With header on the burn-on-read reveal endpoint which allows an authenticated channel member to force the reveal of a burn-on-read message without recipient consent via a crafted Markdown image tag.. Mattermost...

CVE-2026-6339

Mattermost versions 11.5.x = 11.5.1, 11.4.x = 11.4.3 fail to validate the X-Requested-With header on the burn-on-read reveal endpoint which allows an authenticated channel member to force the reveal of a burn-on-read message without recipient consent via a crafted Markdown image tag.. Mattermost...

CVE-2026-6339

Mattermost contains a vulnerability (CVE-2026-6339) in versions 11.5.x <= 11.5.1 and 11.4.x

CVE-2026-6339 Missing request origin validation on burn-on-read reveal endpoint

Mattermost versions 11.5.x = 11.5.1, 11.4.x = 11.4.3 fail to validate the X-Requested-With header on the burn-on-read reveal endpoint which allows an authenticated channel member to force the reveal of a burn-on-read message without recipient consent via a crafted Markdown image tag.. Mattermost...

CVE-2026-6340

Mattermost versions 11.5.x = 11.5.1, 10.11.x = 10.11.13, 11.4.x = 11.4.3 fail to validate 7zip archive structure before processing which allows an authenticated attacker to cause server memory exhaustion and denial of service via uploading a specially crafted 7zip file with excessive folder...